Review Question - QID 102728

This patient most likely has corticosteroid-induced avascular necrosis (AVN) of the femoral head given her hip pain that has been gradually worsening in the setting of treatment for newly-diagnosed sarcoidosis (which often involves administration of steroids). The most sensitive test for this condition is MRI imaging.

Avascular necrosis of the femoral head (also known as osteonecrosis) is caused by infarction of the bone and marrow. Patients present with pain associated with activity without a restricted range of motion or history of trauma. Causes of avascular necrosis include trauma, high-dose corticosteroids, alcoholism, and sickle cell disease. The best initial step in management is typically a radiograph; however, MRI is the most sensitive test, showing a classic "double-line" sign which shows a border of high and low intensity.

Incorrect Answers:
Answer 1: CT of the hip is a very sensitive and specific test for fractures; however, when compared to MRI it is less sensitive/specific for diagnosing osteonecrosis.

Answer 2: Radiograph of the hip is the best initial step for a patient who presents with hip pain as it is a non-invasive (minimal radiation exposure) and rapid test that can rule out any large lesions that could explain the patient's symptoms. It is rarely the most sensitive test for any diagnosis.

Answer 4: Radionuclide scan of the hip is not the best screening test as it shows no increased uptake in early stages and is rather non-specific when making the diagnosis.

Answer 5: Ultrasound of the hip is not used in the diagnosis of avascular necrosis of the hip. It may be used in children younger than 4 months of age to image the hip (such as in developmental dysplasia of the hip).

Bullet Summary:
MRI is the most sensitive test for avascular necrosis.